title: Caesium accumulation in yeast and plants is selectively repressed by loss of the SNARE Sec22p/SEC22.
abstract: The non-essential cation caesium (Cs(+)) is assimilated by all organisms. Thus, anthropogenically released radiocaesium is of concern to agriculture. Cs(+) accumulates owing to its chemical similarity to the potassium ion (K(+)). The apparent lack of a Cs(+)-specific uptake mechanism has obstructed attempts to manipulate Cs(+) accumulation without causing pleiotropic effects. Here we show that the SNARE protein Sec22p/SEC22 specifically impacts Cs(+) accumulation in yeast and in plants. Loss of Saccharomyces cerevisiae Sec22p does not affect K(+) homeostasis, yet halves Cs(+) concentration compared with the wild type. Mathematical modelling of the uptake time course predicts a compromised vacuolar Cs(+) deposition in sec22Δ. Biochemical fractionation confirms this and indicates a new feature of Sec22p in enhancing non-selective cation deposition. A developmentally controlled loss-of-function mutant of the orthologous Arabidopsis thaliana SEC22 phenocopies the reduced Cs(+) uptake without affecting plant growth. This finding provides a new strategy to reduce radiocaesium entry into the food chain.
authors.affiliation: Institute of Radiation Protection, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany. sjohanndraexl@yahoo.com
authors.forename: Stephan
authors.initials: S
authors.lastname: Dräxl
authors.forename: Johannes
authors.initials: J
authors.lastname: Müller
authors.forename: Wei B
authors.initials: WB
authors.lastname: Li
authors.forename: Bernhard
authors.initials: B
authors.lastname: Michalke
authors.forename: Hagen
authors.initials: H
authors.lastname: Scherb
authors.forename: Burkhard A
authors.initials: BA
authors.lastname: Hense
authors.forename: Jochen
authors.initials: J
authors.lastname: Tschiersch
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kanter
authors.forename: Anton R
authors.initials: AR
authors.lastname: Schäffner
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001692:Biological Transport; D002412:Cations; D002586:Cesium / Q000378:metabolism*; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D050683:R-SNARE Proteins / Q000378:metabolism*; D015203:Reproducibility of Results; D012413:Rubidium / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic; D014617:Vacuoles / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002412:Cations; D050683:R-SNARE Proteins; C585280:SEC22 protein, Arabidopsis; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C106909:Sec22 protein, S cerevisiae; D002586:Cesium; D012413:Rubidium